1. Field of the Invention
The present invention relates to an image recording apparatus, and more particularly, to an image stabilizing apparatus and method for compensating a movement of the image recording apparatus to stabilize an image captured by the image recording apparatus.
2. Description of the Related Art
When photographing an object using an image capturing system, e.g., a camcoder, it is difficult to stably photograph the object without trembling of the hands. Such hand trembling may be serious when the image capturing system is small and light so that the user photographs while holding the camcoder with only one hand. Furthermore, as magnifications of zoom lens of the camcoder increases, a photographed image is seriously shaken by a minute movement of the camcoder.
In order to solve the problems, an image stabilizing apparatus for stabilizing the photographed image by automatically correcting tremblings of hands is required. In such an image stabilizing apparatus, the motion of the image capturing apparatus caused by trembling hands is detected by an image detection method. That is, a local motion vector of the image is detected by using a local motion vector detector. Also, a field motion vector representing the motion of an entire field, and an accumulated motion vector representing special circumstances, are detected using the local motion vector.
One of conventional motion detecting methods detects the motion of an image according to a motion of a representative point. In such a method, a predetermined number of representative points are set in a motion detecting area. Then, the motion of the image is estimated by detecting the motion of the predetermined representative points. Even though such a method has an advantage in that it can be implemented by a simple hardware, the method has a drawback in that the precision is deteriorated when there is a moving object in the image.
Another conventional image detecting method uses a band extract representative point (BERP) to detect the motion of the image. According to the motion detecting method using the BERP, characteristic points of an image are extracted by passing the image signal through a band filter in order to enhance the precision as compared with the method using the representative point. Then, the motion of the image is detected by use of the characteristic points. However, this method has a drawback in that the required memory capacity is increased.
Another conventional image detecting method uses edge pattern matching technique. The motion detection method using edge pattern matching technique can be implemented by a simple hardware and reduces the required memory capacity by extracting edge patterns from the image, and thus may overcome the problems of the method using BERP. However, according to this method, the detecting precision may be lowered when the illumination is low. Furthermore, it is difficult to detect the edge from the image.
Therefore, a motion detecting method which can reduce the required memory capacity, while maintaining the degree of precision in motion detection, is required.
To solve the above problems, one of the object of the present invention is to provide an image stabilizing apparatus for correcting motion of an image by bit-plane matching which is capable of precisely detecting motion according to a change in illumination and reducing memory capacity.
Another object of the present invention is to provide an image stabilizing method by using the image stabilizing apparatus.
In order to achieve one of the above objects, there is provided an image stabilizing apparatus for correcting motion of an image recording apparatus by using a bit-plane matching technique, and an image stabilizing method thereof. In the image stabilizing apparatus, a field memory stores input digital image information. A motion detecting circuit calculates an amount of movement of input image information between two screens by using bit-plane matching technique and outputs a motion vector of the image recording apparatus. A motion correcting circuit corrects the motion of the image recording apparatus by moving image information stored in the field memory in an opposite direction to the direction of the motion vector.
In order to achieve another one of the above objects, there is provided an image stabilizing method in an image recording apparatus, the method comprises the steps of: (a) detecting a motion vector of an input image using a bit-plane matching technique; and (b) correcting the motion of an image recording apparatus by moving the input image in the opposite direction to a direction of the detected motion vector.
Preferably, the step (a) comprises the steps of: (a1) extracting bit-planes from digital image information; (a2) selecting an optimum bit-plane among the extracted bit-planes; (a3) storing the optimum bit planes of a previous screen and a current screen; (a4) comparing pixel values of the optimum bit-plane of a previous screen stored in the bit-plane memory and pixel values of the optimum bit-plane in a current screen to calculate correlation values between the pixels bit-planes, and accumulating the calculated correlation values; and (a5) calculating the motion vector from the accumulated correlation value.